A transparency, also known variously as a viewfoil, foil, or viewgraph, is a thin sheet of
transparent flexible material, typically
polyester
Polyester is a category of polymers that contain the ester functional group in every repeat unit of their main chain. As a specific material, it most commonly refers to a type called polyethylene terephthalate (PET). Polyesters include natura ...
(historically
cellulose acetate
In biochemistry, cellulose acetate refers to any acetate ester of cellulose, usually cellulose diacetate. It was first prepared in 1865. A bioplastic, cellulose acetate is used as a film base in photography, as a component in some coatings, and ...
), onto which figures can be drawn. These are then placed on an
overhead projector
An overhead projector (often abbreviated to OHP), like a film or slide projector, uses light to project an enlarged image on a screen, allowing the view of a small document or picture to be shared with a large audience.
In the overhead projec ...
for display to an audience. Many companies and small organizations use a system of projectors and transparencies in meetings and other groupings of people, though this system is being largely replaced by
video projectors and
interactive whiteboard
An interactive whiteboard (IWB), also known as interactive board or smart board, is a large interactive display board in the form factor of a whiteboard. It can either be a standalone touchscreen computer used independently to perform task ...
s.
Printing
Transparencies can be printed on
laser printer
Laser printing is an electrostatic digital printing process. It produces high-quality text and graphics (and moderate-quality photographs) by repeatedly passing a laser beam back and forth over a negatively-charged cylinder called a "drum" to ...
s or
copiers. Specialist transparencies are available for use with laser printers that are better able to handle the high temperatures present in the fuser unit. For inkjet printers, coated transparencies are available that can absorb and hold the liquid ink—although care must be taken to avoid excessive exposure to moisture, which can cause the transparency to become cloudy; they must also be loaded correctly into the printer as they are only usually coated on one side.
Uses
Uses for transparencies are as varied as the organizations that use them.
Certain classes, such as those associated with
mathematics
Mathematics is an area of knowledge that includes the topics of numbers, formulas and related structures, shapes and the spaces in which they are contained, and quantities and their changes. These topics are represented in modern mathematics ...
or
history
History (derived ) is the systematic study and the documentation of the human activity. The time period of event before the invention of writing systems is considered prehistory. "History" is an umbrella term comprising past events as well ...
and
geography
Geography (from Greek: , ''geographia''. Combination of Greek words ‘Geo’ (The Earth) and ‘Graphien’ (to describe), literally "earth description") is a field of science devoted to the study of the lands, features, inhabitants, an ...
use transparencies to illustrate a point or problem. Until the advent of
LaTeX
Latex is an emulsion (stable dispersion) of polymer microparticles in water. Latexes are found in nature, but synthetic latexes are common as well.
In nature, latex is found as a milky fluid found in 10% of all flowering plants (angiosperms ...
, math classes in particular used rolls of acetate to illustrate sufficiently long problems and to display mathematical symbols missing from common computer keyboards.
Aerospace companies, like
Boeing
The Boeing Company () is an American multinational corporation that designs, manufactures, and sells airplanes, rotorcraft, rockets, satellites, telecommunications equipment, and missiles worldwide. The company also provides leasing and ...
and
Beechcraft
Beechcraft is an American brand of civil aviation and military aircraft owned by Textron Aviation since 2014, headquartered in Wichita, Kansas. Originally, it was a brand of Beech Aircraft Corporation, an American manufacturer of general avi ...
, used transparencies for years in management meetings in order to brief engineers and relevant personnel about new aircraft designs and changes to existing designs, as well as bring up illustrated problems.
Some churches and other religious organizations used them to show sermon outlines and illustrate certain topics such as
Old Testament
The Old Testament (often abbreviated OT) is the first division of the Christian biblical canon, which is based primarily upon the 24 books of the Hebrew Bible or Tanakh, a collection of ancient religious Hebrew writings by the Israelites. The ...
battles and
Jewish
Jews ( he, יְהוּדִים, , ) or Jewish people are an ethnoreligious group and nation originating from the Israelites Israelite origins and kingdom: "The first act in the long drama of Jewish history is the age of the Israelites""The ...
artifacts during worship services, as well as outline business meetings.
Spatial light modulators (SLMs)
Many
overhead projector
An overhead projector (often abbreviated to OHP), like a film or slide projector, uses light to project an enlarged image on a screen, allowing the view of a small document or picture to be shared with a large audience.
In the overhead projec ...
s are used with a flat-panel
LCD which, when used this way, is referred to as a
spatial light modulator
A spatial light modulator (SLM) is an object that imposes some form of spatially varying modulation on a beam of light. A simple example is an overhead projector Transparency (projection), transparency. Usually when the term SLM is used, it means ...
or SLM. Data projectors are often based on some form of SLM in a projection path. An LCD is a transmissive SLM, whereas other technologies such as Texas Instrument's
DLP are reflective SLMs. Not all projectors use SLMs (e.g., some use devices that produce their own light rather than function as transparencies). An example of non-SLM system are
organic light-emitting diode
An organic light-emitting diode (OLED or organic LED), also known as organic electroluminescent (organic EL) diode, is a light-emitting diode (LED) in which the emissive electroluminescent layer is a film of organic compound that emits light i ...
s (OLEDs).
See also
*
Presentation slide
A slide is a single page of a presentation. Collectively, a group of slides may be known as a slide deck. A slide show is an exposition of a series of slides or images in an electronic device or in a projection screen.
Before the advent of the p ...
*
Projection panel
*
Reversal film
In photography, reversal film or slide film is a type of photographic film that produces a positive image on a transparent base. Instead of negatives and prints, reversal film is processed to produce transparencies or diapositives (abbreviat ...
References
{{Authority control
Display technology
Office equipment
Presentation